Kinetic studies on enhancement of degradation of chlorpyrifos and its hydrolyzing metabolite TCP by a newly isolated Alcaligenes sp JAS1

JAS1 bacterial strain capable of degrading chlorpyrifos and its major metabolite 3,5,6-trichloro-2-pyridinol (TCP) were isolated from paddy field soil. The isolated bacterial strain was characterized using morphological and biochemical analysis, as well as molecular characterization based on 16S rRNA sequence homology which confirmed its identity as Alcaligenes sp. The isolated bacterial strain efficiently degraded 300 mg/l of chlorpyrifos within 12 h of incubation and TCP was observed to accumulate in the aqueous medium. In soil studies with nutrients amendment along with chlorpyrifos and Alcaligenes sp. JAS1 showed undetectable level of pesticide in 24 h, whereas in the absence of nutrients the pesticide was found to be degraded in 48 h. Kinetic studies based on various models were carried out and the results showed a very good compliance with the first and pseudo first order models. TCP degradation process by Alcaligenes sp. JAS1 was characterized by the rate constant (k) of 1.364 d(-1) and the initial concentration was reduced by 50% (DT50) was 0.5 d in the aqueous medium. Studies on biodegradation of TCP in soil with nutrients showed that JAS1 strain exhibited efficient degradation with a rate constant of 1.137 d(-1), and DT50 was 0.6 d. In contrast, degradation of TCP in soil without nutrients was characterized by a rate constant of 0.953 d(-1) and DT50 was 0.7 d. (C) 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.